|  | 1.4 | Network Layer Functions
| 1.4.5 | Types of ICMP messages
ICMP messages are carried in IP datagrams and are used to send error and control messages. ICMP uses the following types of defined messages; others exist, but are not included on this list: Destination unreachable Time exceeded Parameter problem Source quench Redirect Echo Echo reply Timestamp Timestamp reply Information request Information reply Address request Address reply